linux-kernel - Re: [PATCH 1/3] Add flag to identify block swap devices

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Date:	Fri, 07 May 2010 13:46:43 +0530
From:	Nitin Gupta <ngupta@...are.org>
To:	jassi brar <jassisinghbrar@...il.com>
CC:	Greg KH <greg@...ah.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Pekka Enberg <penberg@...helsinki.fi>,
	Hugh Dickins <hugh.dickins@...cali.co.uk>,
	Cyp <cyp561@...il.com>, Minchan Kim <minchan.kim@...il.com>,
	linux-kernel@...r.kernel.org, Al Viro <viro@...iv.linux.org.uk>
Subject: Re: [PATCH 1/3] Add flag to identify block swap devices

On 05/07/2010 01:33 PM, jassi brar wrote:
> On Fri, May 7, 2010 at 4:25 PM, Nitin Gupta <ngupta@...are.org> wrote:
>> Added SWP_BLKDEV flag to distinguish block and regular file backed
>> swap devices. We could also check if a swap is entire block device,
>> rather than a file, by:
>> S_ISBLK(swap_info_struct->swap_file->f_mapping->host->i_mode)
>> but, I think, simply checking this flag is more convenient.
> This might make it convenient for now but is likely to increase complexity and
> redundancy. Why not define a macro/inline to figure that out?
> 

Accessing such long pointer chain is maybe not good thing to do for
every swap_entry_free() call? Simple checking a flag is perhaps slightly
faster? I also can't see how this flag can later increase complexity
compared to creating new macro for this check.

Thanks,
Nitin
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